Battery Question

Submitted: Sunday, Jan 09, 2005 at 10:48

ThreadID: 19201 Views:2189 Replies:4 FollowUps:6

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chappobriz

Hi All,
I have a question about batteries. I have been given a 38ah deep cycle battery. I want to use it to power lighting for my camper trailer and have been reading about how to install it etc (dual/andersonplugs etc). My question is as follows-
I use a LED light (60 LED's ) that I beleive draws .5 amps. (it says on it 2.4 watts or something). How long will this battery power this light for- is it 76 hours? If it is close to this then I will just buy an electric battery charger to charge it up as we only camp away from power for a maximum of one week and a plugin charger is going to be cheaper than setting up the second battery in the car or trailer. Is my thinking clear here or am I missing something?

We leave next week for a 2 month trip from Brisbane around SA and across ocean road and back up the coast. We have friends etc to drop in at and stay to break up the camping for my girls (XX y.o., 3 y.o and 4 months!) and would just re-charge the battery at stopovers!.
Any thoughts from forumites would be much appreciated.
Regards
Wayne Chapman

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Reply By: Magnus - Sunday, Jan 09, 2005 at 13:25

Sunday, Jan 09, 2005 at 13:25

Wayne,

If the light is 2.4 watts it draws .2 of an amp. You will probably only want to run the battery down to 20 ah so you will still get over 70 hours from a technical draw down of 18 a/hrs, (actually 90 hrs). But it will be a lot less, like could be up to 25% less if the battery is not fully and properly charged. So even if you end up with say only 60 hrs available that is still 15 nights at 4 hrs night.

So, you will probaly be OK. seeing as there won't be many nights in a row without power.

While the arrangement you suggest will certainly be a lot cheaper than going the second battery route for the limited non powered camping you do, bear in mind that recharging your free deep cycle with an el cheapo battery charger is not the recommended approach for charging deep cycle batteries. It will shorten its life.

There are some useful links at this site that will help you.

Cheers, and enjoy the trip. I am in Brisbane also.

Magnus

AnswerID: 92037

Follow Up By: chappobriz - Monday, Jan 10, 2005 at 00:52

Monday, Jan 10, 2005 at 00:52

Thanks Magnus-most informative. WHy is charger not as beneficial to a deep cycle battery?
Wayne

FollowupID: 350914

Follow Up By: Magnus - Monday, Jan 10, 2005 at 09:41

Monday, Jan 10, 2005 at 09:41

Check out this site

Batteries

and this one

Another

and this one

Home

where there is plenty of info on batteries and charging specifically deep cycle batteries.

Magnus

FollowupID: 350945

Reply By: Member - Jimbo (VIC) - Sunday, Jan 09, 2005 at 14:15

Sunday, Jan 09, 2005 at 14:15

Wayne,

You might consider a very small solar panel. The likes of Repco knock one out for about $40, designed to maintain charge in batteries. May put in enough for your needs and maintain the life of your battery.

Cheers,

Jim.

AnswerID: 92048

Follow Up By: chappobriz - Monday, Jan 10, 2005 at 00:53

Monday, Jan 10, 2005 at 00:53

Jim,
Do Repco sell them for that cheap? What else do you need? Do you just hook up the panel to the positive terminal?
Chappo

FollowupID: 350915

Follow Up By: Member - Jimbo (VIC) - Monday, Jan 10, 2005 at 07:25

Monday, Jan 10, 2005 at 07:25

My understanding is they simply have two crocodile clips to attach to the battery terminals and there is no need for a regulator as the output is very low. You'll just need to check that the actual output from the panel. Although as Magnus said you've probably got many days anyway.

I think they are then safe to leave attached to your battery when at home to keep it fully charged, therefore no need to buy a charger. But you'll need to check that out, I'm no expert.

Cheers,

Jim.

FollowupID: 350924

Follow Up By: Member - Jimbo (VIC) - Monday, Jan 10, 2005 at 17:49

Monday, Jan 10, 2005 at 17:49

Wayne,

I saw one today at Supercheap and it is rated at 100 m/ah. Therefore it would need 10 hours of good sun to produce 1 amp and a lot less on an overcast day. However given that you may be using as little as .8 anps per day, it should keep up.

Cheers,

Jim.

FollowupID: 351052

Follow Up By: chappobriz - Monday, Jan 10, 2005 at 18:45

Monday, Jan 10, 2005 at 18:45

Jim,
How much were they do you know?
Wayne

FollowupID: 351064

Reply By: Wok - Monday, Jan 10, 2005 at 06:56

Monday, Jan 10, 2005 at 06:56

Chappobriz,

If you tested the combination you would know the peformance. The maths won't tell you the current condition of the battery.

With a standard [refillable] wetcell the specific-gravity readings would give you a pretty accurate reading for state-of-charge [voltage isn't as good]. The SOC vs specific gravity graph is a straight line, so you nead only 3 readings,say 2 days apart and you could work out the perfomance from full-charge to 'flat' [ you don't need to start from full-charge]

cheers

AnswerID: 92118